This invention relates generally to rollers used in leveling paved or unpaved surfaces. More particularly, this invention concerns a vibratory roller having a variable amplitude of vibration.
In the past, vibratory rollers have been provided with vibrators which include a shaft having a variably positionable eccentric mass. Usually, the variable eccentric mass is adjustable between a plurality of discrete radial positions in order to vary the amplitude of vibration of the roller. In the past, problems existed because of the necessity of stopping the vibrating mechanism in order to adjust the position of the eccentric mass for increasing the amplitude of vibration. Also, the eccentric mass was adjustable between only a few positions within its range of travel, thereby minimizing the available choices of vibratory amplitude.
A significant advance in the art was proposed in U.S. Pat. No. 4,105,356, issued to Loveless on Aug. 8, 1978, and assigned to the assignee of this invention. That patent discloses a fluid system which enables the eccentric weight to be adjusted while the vibratory mechanism is operating, and which provides for an infinite number of positions of adjustment of the mass within its travel range. The fluid system includes a storage reservoir for fluid and a conduit arrangement for connecting the reservoir with an outer end of a chamber containing the eccentric mass. During operation of the vibrating mechanism, the eccentric mass pressurizes the fluid in the outer portion of the chamber, under the urging of centrifugal force. Thus, by operator actuation of a valve in the fluid system to communicate such pressurized fluid with the reservoir, the fluid is ejected from the chamber by the mass, enabling the mass to travel outwardly to any new position in order to increase the amplitude of vibration.
The fluid system includes an indicator visible to the operator to indicate the position of the mass. By viewing the indicator, the operator can monitor the movement of the mass and can close the valve when the desired amplitude of vibration is attained.
While the system proposed in the Loveless patent constitutes a significant step forward, room for improvement remains. For example, it would be desirable to have the eccentric mass automatically stop at a desired position of adjustment without the need for the operator to monitor movement of the mass. It would also be desirable to simplify the system, as by eliminating the need for a hydraulic pump, external fluid storage reservoir, and hydraulic conduits for example.